1967/1969 Bonnie Rebuild Desert Sled Project - Any Advice

Hi,

I am new to the forum. I’ve some experience with motorcycles, first Bultaco Pursangs in the 1970’s, then on to BMW bikes. I had a K75S and rebuilt most of it. Then onto a K1300S, perfect shape and very fast and smooth - passed on to another rider in 2019.

I’m in the northern part of Virgina, in the USA.

Now those have gone and I’ve recently acquired a Triumph T120R. The bike is a 1967 T120R Bonneville frame (DU49062) and the engine from a 1969 T120R (EC 19971). It has been in storage for the past 30 years or so. It was rebuilt in about 1982, with a Routt 800cc big barrel kit. Apparently it wasn’t ridden much after then, the owner being in the military and moving around a bit while the bike was in storage.

So I am trying to decide how to best approach this beast. The Amal monobloc dual carburetors are off the bike, and they have the numbers of “10 66” and “389/95” written on the intake flanges. So I am wondering where to get a rebuild kit for these carburetors - or perhaps new carburetors?

Since the bike was rebuilt in 1982 and not ridden much after, I was thinking of just trying to rebuild the carbs and install them and do a good change of oil and fluids and such and trying to give the bike a go - that is see if I can get it running.

The gas tank is rusted out so I need a new tank. I was looking for something simple, and saw some of the tanks for sale on eBay from India. I’ve heard these are not so great. Although I see they also have an alloy/aluminun tank that looks pretty nice.

I am not trying to restore this bike, but just get it running and ridable - with a look to it being a bit more of a scrambler/desert sled style.

So I am wondering if any of you might know the provenance of the carburetors and/or where to get a rebuild kit for them. Also, any suggestions or a replacement gas tank?

Thanks for any advice. I imagine this forum has a number of threads that will have some great information. I will appreciate any of you having some advice or suggestions about the best places to go for parts and information.

Thank you!

 

Well, it looks like my Amals have some more problems that anticipated. The slides are corroded and would need to be replaced as there is a hole in one of them. So as I put together the parts list of rebuilding and repairing the Amals, versus getting some new Mikunis or Amals and I wonder if in the long run I'd be better off with something new.

 

Thanks Joe. I'mm inclined toward the Mikunis at this point, particularly these from MAP - http://www.mapcycle.com/map0359-1-bonneville-69-72-30mm-mikuni-kit.html

 

OK, I have another question regarding carburetors with my bike. I was talking today to a work colleague who at one time converted his bonneville twin with 2 carbs to a single carb with a 2 into 1 manifold. I have done some looking on this and other forums and there is some instruction on this, however I can't seem to find where one might purchase this kind of manifold. I have seen where heads have been swapped out, twin for single carb heads. So I am wondering if anyone has made this change with the 2 into 1 manifold? Thanks.

 

Thanks Darkman. Taking a look at the notes I wrote from the discussion I had with my colleague, I believe he had a 1970/72 500 motor, which may have had a head that allowed him to use the 2 into 1 manifold. I will stick with a twin carb setup for now as I'd like to use as much of the original bike that I can - unless a change will make things a lot easier or more efficient.

 

Thanks. I've decided this also. Now to choose which ones.

 

Speedo and Tach for 1967-1969 Bonneville - is there a way to install a digital speedometer and tachometer for a unit twin 67-60 vintage? I am wondering it anyone has installed a digital tachometer and speedometer, or a combination speedo/tach, on a vintage Triumph. I am not looking for a vintage look necessarily, just wondering if this is something that can be done - and if so what kind of work does it entail? Thanks.

 

I've made a bit of progress. Finally removed the head and cylinder. Found that the pistons are probably beyond help and the cylinder may need replacing as it seems to have already had a coupe of overbores, the pistons revealing 060 on their domes. So now I believe I will need a new cylinder, pistons, etc. I've been looking at the Morgo 750 as well as what they have on M.A.P. cycles. Additionally I am considering whether or not to redo the head myself or send it out for a rebuilding since that is a critical part and I've little experience with installing valve guides and valves, etc. Any comments are appreciated on replacing the cylinder as well as any other items. I will continue to take the engine apart and examine other parts for damage, like rods, etc. Thanks.

 

So I made some progress on my engine tear down on the primary side. I got stopped when I tried to take the rotor off the crankshaft. I don’t have a 2-jaw puller and it did not come off on its own - so I’ll have to get the 2-jaw puller soon to get the primary chain off. I found some parts of very tiny springs in the oily bottom of the primary case. I’m wondering if any of you might know what these could be and what kinds of problems this might indicate with the engine? Thanks.

 

Thanks for the comment on the spring. I was out of town for a bit so glad to get back to it.

 

The last few days I made some more progress on my tear down. I’ve got the primary side off as well as the timing and transmission. I was initially stalled by the rotor, but was able to get a 3 jaw puller to get it off.

I noticed a small crack in the primary cover, it doesn’t go all the way through - wondering if this looks of or should I have it fixed?

The crank end on the primary side was hard coming off, it seems the reason might be that the end was a bit bunged up. The primary chain tensioner didn’t appear to have much wear - so perhaps it had been adjusted properly and is still in good shape? The drive sprocket seems to have some wear. Whoever build this before used a lot of goop on top of gaskets!

I had some difficulty getting the advance off as the interior threads would not take my puller. Looking closely it seems they have been damaged, so this should probably be replaced.